or 8-13% Al, 44-4% H2SO4 and 48-64% of water, its index of basicity being 5-45.
With the simple basic sulphate, A12(SO4)2(OH)2, the index of basicity is 3-62
and with A12(SO4)(OH)4, 1-81.
Commercial sulphates of good quality should not contain more than i%
of insoluble matter, and their content of iron is usually very small (0-0002-
0-005%). F°r turkey-red dyeing their iron content should not exceed 0-001%,
whilst for cotton printing as much as 0-05% is allowed.
The free sulphuric acid varies usually from 0-2 to i% and is, of course, absent
from the basic sulphates. The presence of zinc is always harmful, but it is
NH3 = 17-03 (17)
Ammonia is commonly sold in aqueous solution, D = 0-910, containing
25% by weight of NH3; the strongest solution, D =0-880, contains about
35'8 % NH3. The pure solution is colourless and has a pure ammonia
smell, whereas the technical product may be yellowish and has a more
or less pronounced empyreumatic odour.
Liquefied ammonia is also sold and is prepared by liquefying the gas
in steel cylinders. It contains 97-99% of NH3, besides water, traces of
ammonium salts and lubricating oil from the compressor.
The commonest impurities of ammonia solution consist of chlorides,
sulphates, carbonates, copper, lead, iron, zinc, lime, pyridine bases and
tarry products, which are detected as below. The ammonia content is
determined as in 5.
1. Chlorides, Sulphates.—10-20 c.c., rendered acid with dilute nitric
acid, should not be rendered turbid by silver nitrate (chlorides) or by barium
chloride, even after 12 hours (sulphates).
2. Carbonates.—10 c.c., mixed with 30 c.c. of lime water, should not
3. Metals.—10 c.c., diluted with 40 c.c. of water, should not be ren-
dered coloured or turbid by hydrogen sulphide (copper, lead, iron, zinc)
or ammonium oxalate (calcium).
20 c.c. should leave no appreciable residue on evaporation.
4. Pyridine Bases, Tarry Products.—-These may be detected by
the smell, especially after exact neutralisation of the ammonia with dilute
10 c.c., rendered acid with 20 c.c. of pure i : 3 sulphuric acid (which
does not decolorise permanganate), should be persistently coloured by I
drop of decinormal permanganate.
2 c.c., added to 4 c.c. of nitric acid, should give a colourless liquid leaving
a white residue on evaporation on a steam-bath.
5. Quantitative Determination of the NH3.—The proportion of
ammonia in the solution may be found from the specific gravity or by
titration with a normal acid in presence of methyl orange (i c.c, N-a.cid
= 0-017 gram NH3).applicable to sulphates containing less than 0-25% Fe ;